Extrinsic and intrinsic motivation is key to most employment situations. Extrinsic motivation might involve a good parking space related to a better position at work, a higher salary, or maybe the smile on the face of a patient when you, the doctor, helps them feel better. These things however, have a utility value which can depreciate over time. At a certain point it doesn't matter how much money a job can earn you, you just don't find its overall utility to be worth it. This is where intrinsic motivation can help. Intrinsic motivation is something that requires no external reward or benefit, one is motivated toward a specific action for its own sake. So a doctor that has become bored with the monotonous nature of certain aspects of his job would have to experience increased intrinsic motivation to balance the discounted utility of his position.